Heat transfer apparatus

ABSTRACT

A heat transfer apparatus includes: an evaporating portion that evaporates a working medium by heat of an exhaust gas from an internal combustion engine; a condensing portion that condenses the working medium having been evaporated; a circulation path portion that causes the working medium to circulate between the evaporating portion and the condensing portion; a heat storage member that is provided within the evaporating portion; and a supplying and collecting portion that supplies the working medium to the evaporating portion when the internal combustion engine starts, and that collects the working medium having been condensed when the internal combustion engine stops such that the working medium having been condensed does not contact with the heat storage member.

TECHNICAL FIELD

The present invention relates to a heat transfer apparatus.

BACKGROUND ART

There is a technique in which a liquid-phase working medium is evaporated by use of heat of exhaust gases from an internal combustion engine, heat of the evaporated working medium is condensed, and the condensation heat generated at that time is used for, for example, the warming-up of the internal combustion engine, a heater, or the like. Patent Document 1 discloses a technique in which a heat storage member for storing heat of the evaporated working medium is used as a heat source for evaporating the working medium at the next time when the internal combustion engine starts. Also, Patent Documents 2 to 5 disclose related techniques.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Application Publication No. 2008-255945

PTL 2: Japanese Patent Application Publication No. 2008-292116

PTL 3: Japanese Patent Application Publication No. 2012-255577

PTL 4: Japanese Patent Application Publication No. 2006-183943

PTL 5: Japanese Patent Application Publication No. 2006-183942

SUMMARY OF INVENTION Technical Problem

If the heat storage member radiates heat from the time when the internal combustion engine stops to the time when the internal combustion engine restarts, the heat storage member might not be effectively used as the heat source at the next time when the internal combustion engine starts.

Therefore, the present invention has an object to provide a heat transfer apparatus suppressing heat radiation of a heat storage member.

Solution to Problem

The above object is achieved by a heat transfer apparatus including: an evaporating portion that evaporates a working medium by heat of an exhaust gas from an internal combustion engine; a condensing portion that condenses the working medium having been evaporated; a circulation path portion that causes the working medium to circulate between the evaporating portion and the condensing portion; a heat storage member that is provided within the evaporating portion; and a supplying and collecting portion that supplies the working medium to the evaporating portion when the internal combustion engine starts, and that collects the working medium having been condensed when the internal combustion engine stops such that the working medium having been condensed does not contact with the heat storage member, wherein an inside of the evaporating portion is brought into a vacuum state, when the internal combustion engine stops and the working medium is collected by the supplying and collecting portion, the evaporating portion is provided at its inside with a flow pipe in which the exhaust gas flows from the internal combustion engine, and the heat storage member is arranged within the evaporating portion not to be in contact with the flow pipe.

The evaporating portion may include: a housing that surrounds the flow pipe and the heat storage member; and a supporting portion that supports the heat storage member not to be in direct contact with an inner surface of the housing.

An area, close to the heat storage member, of the supporting portion may be smaller than an area, close to the inner surface of the housing, of the supporting portion.

The supporting portion may be made of a heat insulation material.

Evaporation of the working medium in the evaporating portion and condensation of the working medium in the condensing portion may be repeated to circulate the working medium in the circulation path portion.

The supplying and collecting portion may include: a tank opened to an atmosphere, and storing the working medium in a liquid-phase state; a supplying and collecting path portion communicating the tank with the circulation path portion or with the evaporating portion; and an opening and closing valve provided in the supplying and collecting path portion, a pressure within the circulation path portion and the evaporating portion becomes greater than atmospheric pressure, while the internal combustion engine drives, the working medium having been condensed is absorbed into the tank by opening the opening and closing valve, when the pressure within the circulation path portion and the evaporating portion is greater than the atmospheric pressure.

Advantageous Effects of Invention

According to an aspect of the present invention, it is possible to provide a heat transfer apparatus suppressing heat radiation of a heat storage member.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration view of a heat transfer apparatus;

FIGS. 2(A) and 2(B) are explanatory views of an evaporating portion;

FIG. 3 is a flow chart of an example of control performed by an ECU;

FIG. 4 is a timing chart corresponding to FIG. 3; and

FIGS. 5(A) to 5(C) are explanatory views of variations of the evaporating portion.

DESCRIPTION OF EMBODIMENTS

FIG. 1 is a schematic view of a heat transfer apparatus 1A. FIG. 1 illustrates the heat transfer apparatus 1A, an engine 50, an exhaust pipe 51, a starter converter 52, and an underfloor converter 53. These components illustrated in FIG. 1 are mounted on a vehicle not illustrated. The heat transfer apparatus 1A is equipped with a circulation path portion 10, a diverging path portion 20, a reserve tank 30, and an ECU 40A. In the heat transfer apparatus 1A, heat is transferred by a phenomenon in which a working medium is evaporated by receiving heat and is condensed by radiating heat.

The circulation path portion 10 is provided with a supplying pipe 13 and a returning pipe 14 that connect between an evaporating portion 11 and a condensing portion 12. In the circulation path portion 10 and the evaporating portion 11, the working medium is enclosed beforehand in a state where a pressure thereof is reduced lower than atmospheric pressure (for example, in a state where the pressure thereof is reduced lower than atmospheric pressure by 100 kPa). Therefore, the boiling point of the working medium is adjusted to be suitable for an operating environment, in order to transfer heat by means of the working medium. Specifically, the working medium is H₂O.

A heat exchanger that evaporates the working medium is arranged in the evaporating portion 11, as will be described in later in detail. Specifically, the heat exchanger collects heat from the exhaust gases by exchanging heat between the working medium and the exhaust gases from the engine 50, and evaporates the working medium. Also, a heat storage member H is arranged within the evaporating portion 11, as will be described later in detail.

The starting of the engine 50 is an operation start requirement to start the heat transfer apparatus 1A. The stopping of the engine 50 is an operation stop requirement to stop the heat transfer apparatus 1A. Moreover, after the operation stop requirement is satisfied, the cooling proceeds and then the condensation of the working medium proceeds, so that the circulation path portion 10 is brought into a vacuum state.

The exhaust gases from the engine 50 are purified by the starter converter 52 and the underfloor converter 53 installed in the exhaust pipe 51, and then are discharged therethrough. The evaporating portion 11 is specifically provided in the exhaust pipe 51 at the downstream side of the underfloor converter 53.

The working medium having been evaporated is condensed in the condensing portion 12. The condensing portion 12 is a portion that utilizes heat transferred by the evaporated working medium. For example, the condensing portion 12 is a portion that is provided in the engine 50 and that utilizes heat carried by steam for the warming-up of the engine 50. Therefore, the heat transfer apparatus 1A shares the condensing portion 12 with the engine 50. The condensing portion 12 may be a portion that is provided in the engine 50 and that is capable of reducing friction torque thereof in a cold state of the engine 50 by heat carried by steam. For example, the condensing portion 12 may be a bearing portion of a crank shaft of the engine 50. Also, the condensing portion 12 may be provided to be in contact with a cylinder head or a cylinder block of the engine 50. Also, the condensing portion 12 may be used for heating up a vehicle interior. The condensation heat of the working medium in the condensing portion 12 may be used in other ways, instead of the above one. Also, this heat transfer apparatus may use a rankine cycle system in which a turbine is rotated by a heat pipe or steam.

The supplying pipe 13 supplies steam from the evaporating portion 11 to the condensing portion 12. The returning pipe 14 returns the condensed working medium from the condensing portion 12 to the evaporating portion 11. Specifically, the returning pipe 14 is provided to return the condensed working medium from the condensing portion 12 to the evaporating portion 11 by gravity.

A pressure sensor 61 and a temperature sensor 62 are installed in the supplying pipe 13. The pressure sensor 61 detects the pressure within the circulation path portion 10 by detecting the pressure within the supplying pipe 13. The temperature sensor 62 detects the temperature within the circulation path portion 10 by detecting the tem- perature within the supplying pipe 13.

Further, the pressure sensor 61 is located at the highest position in the circulation path portion 10. Also, the temperature sensor 62 is provided for detecting the internal temperature within a portion of the circulation path portion 10 in which the pressure sensor 61 detects the system internal pressure.

The diverging path portion 20 is provided with a diverging pipe 21 and a valve 22. The diverging pipe 21 diverges from the circulation path portion 10. The valve 22 controls the flow rate of the working medium flowing in the diverging pipe 21, and is, for example, a flow rate adjusting valve. However, the valve 22 is not limited to this, and may be an opening and closing valve. The diverging pipe 21 is connected to the reserve tank 30. The reserve tank 30 stores the liquid-phase working medium to be supplied to the circulation path portion 10 and the evaporating portion 11. The diverging pipe 21, the valve 22, and the reserve tank 30 are an example of a supplying and collecting portion that is capable of supplying and collecting the working medium.

Specifically, the diverging pipe 21 is connected to the bottom of the reserve tank 30 from its lower side through the valve 22. Therefore, the diverging pipe 21 is connected to the reserve tank 30 so as to form an opening thereof at a position lower than a height position of a liquid surface to be at least ensured in the reserve tank 30. The diverging pipe 21 diverges from the returning pipe 14 in the upward direction with respect to the gravity direction, and diverges from a portion of the returning pipe 14 close to the evaporating portion 11.

The reserve tank 30 is specifically an atmosphere open type tank in which the working medium stored in the liquid phase state receives atmospheric pressure. The reserve tank 30 has a capacity capable of storing not only the working medium to be stored in the liquid phase state but also the working medium circulating in the circulation path portion 10 in the liquid phase state. For example, the reserve tank 30 may be a tank with a breather valve that is opened by a predetermined pressure so as to suppress an increase in the internal pressure.

The ECU 40A is an electronic controller that is electrically connected with sensors and switches such as not only the pressure sensor 61 and the temperature sensor 62 but also an atmospheric pressure sensor 63 for detecting an atmospheric pressure, an atmospheric temperature sensor 64 for detecting an atmospheric temperature, and sensors 65 for detecting the driving state of the engine 50. Also, the valve 22 is electrically connected as a controlled object.

The sensors 65 include: a crank sensor capable of detecting a rotational speed NE of the engine 50; an airflow meter capable of measuring an intake air amount of the engine 50; an accelerator opening degree sensor detecting an amount of stepping on an accelerator pedal to request acceleration of the engine 50; a water temperature sensor detecting a temperature of cooling water of the engine 50; an exhaust gas temperature sensor detecting a temperature of the exhaust gas of the engine 50; and an ignition switch for starting the engine 50. Various outputs from the sensors 65 and various information based on the outputs from the sensors 65 may be obtained through, for example, an ECU for controlling the engine 50. Alternatively, the ECU 40A may be the ECU for controlling the engine 50.

In the ECU 40A, a CPU processes based on a program stored in a ROM and uses a temporary memory area of a RAM if necessary.

Next, the evaporating portion 11 will be described in detail. FIGS. 2(A) and 2(B) are explanatory views of the evaporating portion 11. The evaporating portion 11 includes a housing 11 a, a heat storage member H arranged within the housing 11 a, and a heat exchanger 60. The exhaust gas flows in the heat exchanger 60 through the exhaust pipe 51. For example, the heat exchanger 60 is a multitubular type, but not limited to this arrangement. The heat exchanger 60 is an example of a flow pipe. Also, such a heat exchanger may be not provided, and the exhaust pipe 51 itself may penetrate through the evaporating portion 11. In this case, the exhaust pipe 51 corresponds to a flow pipe.

The housing 11 a is provided at its inside with the heat storage member H. The heat storage member H may be made of any of materials such as calcium chloride hydrate, sodium sulphate hydrate, sodium acetate hydrate, sodium thiosulfate hydrate, and paraffin.

FIG. 2(A) illustrates a state where the heat storage member H is exposed to the working medium condensed in the evaporating portion 11. FIG. 2(B) illustrates a state where the liquid-phase working medium is collected by the reserve tank 30. As will be described later in detail, the liquid-phase working medium is evaporated in the evaporating portion 11 as illustrated in FIG. 2(A) during the driving of the engine 50. While the engine 50 stops, the liquid-phase working medium is collected by the reserve tank 30 as illustrated in FIG. 2(B), so the liquid-phase working medium does not contact with the heat storage member H, and the inside of the evaporating portion 11 is brought into the vacuum state.

As illustrated in FIG. 2(A), the heat storage member H receives and stores the heat from the working medium boiled by the heat of the exhaust gases. In this case, since the working medium is liquid, the heat of the working medium is stored in the heat storage member H effectively. As will be described later in detail, the heat storage member H is used as a heat source at the time of restarting the engine 50, and the heat radiation of the heat storage member H is suppressed during the stopping of the engine 50 as follows.

While the engine 50 stops, the liquid-phase working medium is collected by the reserve tank 30 so as not to contact with the heat storage member H. This suppresses the heat storage member H from radiating heat through the liquid-phase working medium during the stopping of the engine 50.

Also, while the engine 50 stops, the inside of the evaporating portion 11 is brought into the vacuum state, that is, the internal pressure thereof becomes equal to or lower than atmospheric pressure. In this state, since there is little gas, into which heat is transferred from the heat storage member H, in the vicinity of the heat storage member H, the heat radiation of the heat storage member H is suppressed.

Also, the heat storage member H is supported away from the heat exchanger 60 by a predetermined clearance C. This reason is as follows. While the engine 50 stops, the exhaust gases are not emitted, so that the temperature of the heat exchanger 60 is reduced. In a case where the heat storage member H is in contact with the heat exchanger 60, the temperature of the heat exchanger 60 is reduced after the engine 50 stops, so that the heat exchanger 60 accelerates the heat radiation of the heat storage member H. In the present embodiment, the heat storage member H is not in contact with the heat exchanger 60, thereby suppressing the heat radiation of the heat storage member H during the stopping of the engine 50.

The heat storage member H is supported by pillar portions B so as not to be in contact with an inner surface of the housing Ila and so as to be away therefrom. Specifically, the pillar portions B are arranged between the heat storage member H and an inner bottom surface of the housing 11a and between the heat storage member H and an inner side surface of the housing 11 a. The pillar portions B are secured to the heat storage member H. The heat storage member H is not in contact with the housing 11 a, thereby suppressing the heat radiation of the heat storage member H through the housing 11 a during the stopping of the engine 50. For example, the pillar portion B may be made of metal or heat insulation material. The pillar portion B is an example of a supporting member.

The pillar portion B has a taper shape such that its cross sectional area is gradually decreasing from the heat storage member H toward the inner surface of the housing 11 a. The pillar portion B has a small cross sectional area close to the housing 11 a, thereby suppressing heat from being transferred from the heat storage member H to the housing 11 a through the pillar portions B during the stopping of the engine 50. In addition, the pillar portion B may not have such a taper shape. The pillar portion B may be in point or line contact with the housing 11 a. Also, as for the pillar portion B, the area close to the housing 11 a has only to be smaller than the area close to the heat storage member H.

The pillar portion B supports the heat storage member H at a position away from the inner bottom surface of the housing 11 a by a predetermined height. Therefore, for example, even if the reserve tank 30 cannot collect the liquid-phase working medium sufficiently during the stopping of the engine 50 so that a little liquid-phase working medium remains within the evaporating portion 11, the heat storage member H is prevented from being soaked in the liquid-phase working medium. This suppresses the heat radiation of the heat storage member H.

A thin heat insulation material 11 b is attached to the inner surface of the housing 11 a around the heat storage member H. This suppresses a decrease in the temperature within the housing 11 a, and suppresses the heat radiation of the heat storage member H during the stopping of the engine 50.

FIG. 3 is a flowchart of an example of the control performed by the ECU 40A. Additionally, this control is performed during the stopping of the engine 50. FIG. 4 is a timing chart corresponding to FIG. 3. FIG. 4 illustrates a heat storage state and a heat radiation state of the heat storage member H, opening and closing states of the valve 22, and a state of the pressure within the paths such as the circulation path portion 10 and the evaporating portion 11. Also, in FIG. 4, the state of the working medium within the evaporating portion 11 is simply illustrated in accordance with the timing chart.

The ECU 40A determines whether or not the engine 50 stops on the basis of outputs from a sensor for detecting on/off of the ignition switch (step S1). When negative determination is made, the engine 50 performs the process of step S1 again. While the engine 50 drives, the liquid-phase working medium is evaporated in the evaporating portion 11.

When the engine 50 stops, the ECU 40A determines whether or not the pressure in the system is greater than atmospheric pressure (step 2). When negative determination is made, the ECU 40A finishes these processes. When affirmative determination is made, the ECU 40A controls the valve 22 to open for a predetermined period (step S3), and controls the valve 22 to close afterward (step S4). Therefore, the liquid-phase working medium in the paths are collected by the reserve tank 30. This is because the evaporated working medium causes the pressure in the paths to be greater than atmospheric pressure, the reserve tank 30 is opened to the atmosphere, and the liquid-phase working medium in the paths is absorbed toward the lower pressure side by opening the valve 22. The ECU 40A controls the valve 22 to open only for a period to collect the liquid-phase working medium, and controls the valve 22 to close afterward.

Since the engine 50 stops after the liquid-phase working medium is collected by the reserve tank 30, the temperature of the heat exchanger 60 decreases, that is, the temperature in the paths decreases. Thus, the pressure in the paths decreases to be brought into the vacuum state, that is, the pressure becomes lower than atmospheric pressure.

Next, the ECU 40A detects whether or not the engine 50 restarts (step S5). The starting of the engine 50 is decided based on outputs from the sensor for detecting on/off of the ignition switch. When negative determination is made, the ECU 40A repeats the process of step S5.

When affirmative determination is made, the ECU 40A controls the valve 22 to open for a predetermined period (step S6), and controls the valve 22 to close afterward (step S7). Therefore, the liquid-phase working medium is supplied into the circulation path portion 10 and the evaporating portion 11. This is because the pressure in the paths is lower than atmospheric pressure such that the paths are brought into the vacuum state during the stopping of the engine 50, and the opening of the valve 22 causes the liquid-phase working medium to flow to the circulation path portion 10 and the evaporating portion 11 from the reserve tank 30 opened to the atmosphere. Therefore, the heat storage member H is exposed to the liquid-phase working medium.

As described above, the heat radiation of the heat storage member H is suppressed during the stopping of the engine 50. Thus, the heat storage member H also stores heat at the restarting time. The heat storage member H is soaked into the liquid-phase working medium at the time of restarting the engine 50, so that the heat of the heat storage member H causes the temperature of the liquid-phase working medium to increase. Hence, the heat of the heat storage member H can be used as a heat source at the time of restarting the engine 50. It is therefore possible to evaporate the working medium for a short period of time, even at the time of restarting the engine 50. Accordingly, the warm-up characteristics are improved in restarting the engine 50.

As described above, in the present embodiment, in order to suppress the heat radiation of the heat storage member H during the stopping of the engine 50, the liquid-phase working medium is collected not to contact with the heat storage member H during the stopping of the engine 50, the inside of the evaporating portion 11 is brought into the vacuum state, and further the heat storage member H is supported not to be in contact with the heat exchanger 60.

Additionally, in step S5, the ECU 40A may detect whether or not a door near the driver's seat of a vehicle is opened before the engine 50 restarts. In this case, the ECU 40A may control the valve 22 to open, when it is detected that the door is opened before the engine 50 restarts. In this case, the ECU 40A detects the opened or closed state of the door on the basis of outputs from a sensor for detecting the opening and closing of the door.

FIGS. 5(A) to 5(C) are explanatory views of evaporating portions according to variations. In addition, in FIGS. 5(A) to 5(C), the heat exchanger 60 and the like are omitted, and the evaporating portions are illustrated in the state where the liquid-phase working medium is collected in order to facilitate understanding of the evaporating portions. As illustrated in FIG. 5(A), a heat insulation material 11 b′ is secured to the inside of a housing 11 a′ of an evaporating portion 11′, and the heat storage member H is secured to the insulation material 11 b′ not to be in contact with the housing 11 a′. This suppresses the heat from being transferred from the heat storage member H to the housing 11 a′.

As illustrated in FIG. 5(B), a housing 11 a″ of an evaporating portion 11″ is partially opened, and a heat insulation material 11 b″ is secured to seal an opened portion. The heat storage member H is supported by this insulation material 11 b″. This also suppresses the heat from being transferred from the heat storage member H to the housing 11 a″.

Also, as illustrated in FIG. 5(C), in an evaporating portion 11′″, the heat storage member H is supported away from the inner surface of the housing 11 a by plural insulation materials 11 b′″. This also suppresses the heat from being transferred from the heat storage member H to the housing 11 a. The heat insulation material 11 b′, 11 b″, and 11 b′″ are an example of a supporting member.

While the exemplary embodiments of the present invention have been illustrated in detail, the present invention is not limited to the above-mentioned embodiments, and other embodiments, variations and modifications may be made without departing from the scope of the present invention.

For example, the above embodiment has described that the working medium is H₂O. However, the present invention is not always limited to this arrangement. For example, alcohol may be appropriately used as the working medium. Also, the working medium may not be always enclosed in the circulation path portion in the depressurized state. In this case, for example, the cooling proceeds while the operation stops, so that the condensation of the working medium proceeds, and the circulation path portion has only to be brought into the vacuum state. Also, for example, the heat transfer apparatus may be a rankine cycle apparatus. Further, a pump or the like may supply and collect the liquid-phase working medium.

REFERENCE SIGNS LIST

-   1A heat transfer apparatus -   10 circulation path portion -   11 evaporating portion -   11 a housing -   11 b, 11 b′, 11 b″, 11 b′″ insulation material -   12 condensing portion -   20 diverging path portion -   22 valve -   30 reserve tank -   40A ECU -   H heat storage member -   B pillar portion 

1. A heat transfer apparatus comprising: an evaporating portion that evaporates a working medium by heat of an exhaust gas from an internal combustion engine; a condensing portion that condenses the working medium having been evaporated; a circulation path portion that causes the working medium to circulate between the evaporating portion and the condensing portion; a heat storage member that is provided within the evaporating portion; and a supplying and collecting portion that supplies the working medium to the evaporating portion when the internal combustion engine starts, and that collects the working medium having been condensed when the internal combustion engine stops such that the working medium having been condensed does not contact with the heat storage member, wherein an inside of the evaporating portion is brought into a vacuum state, when the internal combustion engine stops and the working medium is collected by the supplying and collecting portion, the evaporating portion is provided at its inside with a flow pipe in which the exhaust gas flows from the internal combustion engine, and the heat storage member is arranged within the evaporating portion not to be in contact with the flow pipe.
 2. The heat transfer apparatus of claim 1, wherein the evaporating portion includes: a housing that surrounds the flow pipe and the heat storage member; and a supporting portion that supports the heat storage member not to be in direct contact with an inner surface of the housing.
 3. The heat transfer apparatus of claim 2, wherein an area, close to the heat storage member, of the supporting portion is smaller than an area, close to the inner surface of the housing, of the supporting portion.
 4. The heat transfer apparatus of claim 2, wherein the supporting portion is made of a heat insulation material.
 5. The heat transfer apparatus of claim 1, wherein evaporation of the working medium in the evaporating portion and condensation of the working medium in the condensing portion are repeated to circulate the working medium in the circulation path portion.
 6. The heat transfer apparatus of claim 1, wherein the supplying and collecting portion includes: a tank opened to an atmosphere, and storing the working medium in a liquid-phase state; a supplying and collecting path portion communicating the tank with the circulation path portion or with the evaporating portion; and an opening and closing valve provided in the supplying and collecting path portion, a pressure within the circulation path portion and the evaporating portion becomes greater than atmospheric pressure, while the internal combustion engine drives, and the working medium having been condensed is absorbed into the tank by opening the opening and closing valve, when the pressure within the circulation path portion and the evaporating portion is greater than the atmospheric pressure. 